CEntrance Ampersand balanced portable headphone amplifier
Feb 10, 2022 at 6:57 AM Post #46 of 131

ExpatinJapan

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@mgoodman kindly offered to send me a review sample of the Ampersand.

I have been a fan of CEntrance products, performance and sound since the Hifi-m8 crowd designed days - and have reviewed several of their products since.

For Ampersand i referred Michael to another reviewer who i think can do more justice to it than i could - due to their wide experience and understanding of amplifiers and also the hard to drive headphones available to them.

Best to have the right person for the job.

I look forward to reading further impressions and future reviews of the Ampersand.
 
Feb 10, 2022 at 1:15 PM Post #47 of 131

HeadphoneAddict

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I just got my sample (I expected it only next week, so that's good).... It'sso tiny and light compared to the best competitor I already own => the Class A Less BX2+.

Of course, I can't say much about the Ampersand, as I just plugged in the DCA Stealth and the FIIO M17 in pure balanced line-out mode......

I just tried to see what happens when I try to play the monstrous "Cradle to the Grave" from Max Richter => clearly it's still clipping a little between 49" to 1'10" ... as both Ampersand's led indicators turn on Red, I guess that input level is too high with 4V input.
I will try with the Kann Alpha as I can fix the voltage of the balanced line out (I can not on the FIIO M17).

Anyway... everything else I could listen in a pair of hours, really sounded promising !!! even very promising, though battery seems to drop really fast (probably more or less 3 hours ?).
I intend to use the Ampersand with the Sony WM1A (unfortunately with double amp mode), Centrance M8 (BT receiver 2.5mm Line out mode ) or Kann Alpha (4.4mm Line out mode 2V).... For my future trips (Job or Holidays), I still hope it should be the lightest and the best way to enjoy my DCA Stealth when I not at home or office (FIIO M17 is probably more adequate with a desktop stand and external 12V3A power supply) .
Yes, those LEDs are definitely very helpful in tuning the input level that we feed it, so that we don’t overdrive the input. I find that it can accept fairly high input levels before the meters go red and you hear distortion.
 
Feb 10, 2022 at 4:04 PM Post #48 of 131

newworld666

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This evening, I am playing with the Sony WM1A + Ampersand (fix mode)+ HEDDphone One on one side ... and FIIO M17 + HEDDphone One (portable Headphone mode) on the other side...
I am trying to make a kind of A/B comparison, though I didn't have any real expectation with such difficult to drive headphone in low and ultra low frequencies, even the FIIO M17 in portable mode has some real difficulties to compete with his own desktop mode with a dedicated 12V/3A external power supply ?.

So, It seems to be much better than expected as this small Ampersand unit seems really able to produce very clean 2x3W (same power as FIIO M17) and can move rather properly the HEDDphone One.

Probably, my next stage will be against the portable amp Less BX2+... Class A vs Class AB in action.
 
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Feb 10, 2022 at 5:06 PM Post #49 of 131

rodel808

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Anyone can give impressions with the Hifiman HE6v2?
 
Feb 10, 2022 at 5:46 PM Post #50 of 131

mgoodman

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I just tried to see what happens when I try to play the monstrous "Cradle to the Grave" from Max Richter => clearly it's still clipping a little between 49" to 1'10" ... as both Ampersand's led indicators turn on Red, I guess that input level is too high with 4V input.
I will try with the Kann Alpha as I can fix the voltage of the balanced line out (I can not on the FIIO M17).

Anyway... everything else I could listen in a pair of hours, really sounded promising !!! even very promising, though battery seems to drop really fast (probably more or less 3 hours ?).
The RED LEDs in the LED VU meter are calibrated to turn on when the input level is 2V RMS unbalanced or 4V RMS balanced. That's the maximum level Ampersand expects at the input and the amp is calibrated to be nearing clipping at that point (assuming max GAIN and VOLUME settings). So use the VU meter to guide your input levels. Turn down the levels at the DAP/DAC if you see red LEDs coming on a lot and you'll be fine.

Battery should give you more like 4-5 hours and that's with max power into very hungry cans and low dynamic range music, such as thrash metal :wink: Classical with medium hungry cans will do better.
 
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Feb 10, 2022 at 5:53 PM Post #51 of 131

mgoodman

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If it really doesn’t sound as full in medium gain, as he stated, then it would be advised to just set the Ampersand volume to a fixed level at 12 o’clock in high gain, and control the volume with the source; or just use high gain with the volume knob set lower. I still suspect it was possibly a factor of the headphone that was chosen, and with Susvara in high gain you’d still have a wide range of volume knob travel to explore.
Any difference in sound between the medium gain and high gain switch setting is most likely due to how headphones open up with more power. If you raise the Volume with the Volume knob on Medium gain switch setting and lower the Volume with the Volume knob on High switch setting, so that the levels are matched in both cases, you should not hear any difference in SQ as the headphones would be driven with the exact same signal in both cases.

Please note that in the FIX gain setting, the Volume knob up top is disabled and Ampersand takes in full signal, so be careful with the output levels of the DAC/DAP to avoid blowing out the headphones and your ears. The setting of the Ampersand knob in FIX position doesn't matter as the pot is out of the circuit, so you can set it to 7pm, 12 pm or 3pm, etc. -- it won't make any difference in FIX position.
 
Feb 10, 2022 at 6:00 PM Post #52 of 131

mgoodman

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We just received the Quick Start Guides (QSG) for the Ampersand. In a rush to send the units out asap, we didn't place the QSG in some boxes. So if you got the Ampersand and didn't get the Quick Start Guide, here it is attached FYI.


Ampersand-QSG-Page-2-R2-flat.jpg


Ampersand-QSG-Page-1-R2-flat.jpg
 
Feb 10, 2022 at 10:35 PM Post #53 of 131

HeadphoneAddict

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Any difference in sound between the medium gain and high gain switch setting is most likely due to how headphones open up with more power. If you raise the Volume with the Volume knob on Medium gain switch setting and lower the Volume with the Volume knob on High switch setting, so that the levels are matched in both cases, you should not hear any difference in SQ as the headphones would be driven with the exact same signal in both cases.

Please note that in the FIX gain setting, the Volume knob up top is disabled and Ampersand takes in full signal, so be careful with the output levels of the DAC/DAP to avoid blowing out the headphones and your ears. The setting of the Ampersand knob in FIX position doesn't matter as the pot is out of the circuit, so you can set it to 7pm, 12 pm or 3pm, etc. -- it won't make any difference in FIX position.
I think you meant to respond to ChrisLN, as I was saying something very similar.
 
Feb 11, 2022 at 2:21 AM Post #54 of 131

mgoodman

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Just got done testing with DCA Stealth and DCA AEON 2 Noire. Both sound great with the Ampersand. Pictures below.

This was probably the most stringent test. I'm happy with the results.

Aeon has a low 13 Ohm impedance and Stealth is 22 Ohm and slightly less efficient, per Dan Clark. Both of these are very difficult to drive for a portable amp.

These are great headphones and I liked the sound. But sound quality is not what this post is about. As an engineer, I wanted to trip Ampersand's output protection circuit, so I drove these to the point when the circuit tripped and turn off the power to the amp. Basically, if there is an overload condition, rather than damage the amp and cause the user unnecessary frustration, the system just gracefully shuts down the power. The system recovers as soon as the signal level is lowered and this action is not harmful to the operation of the Ampersand or the headphones. We made sure you don't even hear a click. The amp just goes quiet for a moment and then quickly recovers. With the CANJAM LA prototype, level was adequate, but since then, we made significant improvements before going to production. I tested with the shipping, production Ampersand.

Both headphone models get unbearably loud for my taste. I drove the inputs into clipping so I could see the RED LEDs, switched the gain to MAX and raised the Volume so I could engage the output short circuit protection and it would cut out. Listening levels were so uncomfortably loud at that point that I could only stand it for about 10 seconds. I would NEVER EVER listen at that level. When I backed the Volume down to the level at which I could listen for more than 10 seconds, the amp performed completely fine.

So here is the list of headphones we successfully tested to date with Production Ampersand:

Aeon 2 Noir, Stealth, Susvara, Ananada, HE-6, HD-800/800s, and HEDD.

I expect more are coming shortly. All preorder units are likely already received by their customers.

Ampersand-with-DCA Stealth-1200x900.jpg


Ampersand-with-Aeon-2-Noire-955x1200.jpg


Ampersand-RED-LED-912x1200.jpg
Ampersand-with-Stealh-800x800.jpg
 
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Feb 11, 2022 at 2:40 AM Post #55 of 131

ChrisLN

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Any difference in sound between the medium gain and high gain switch setting is most likely due to how headphones open up with more power. If you raise the Volume with the Volume knob on Medium gain switch setting and lower the Volume with the Volume knob on High switch setting, so that the levels are matched in both cases, you should not hear any difference in SQ as the headphones would be driven with the exact same signal in both cases.

Please note that in the FIX gain setting, the Volume knob up top is disabled and Ampersand takes in full signal, so be careful with the output levels of the DAC/DAP to avoid blowing out the headphones and your ears. The setting of the Ampersand knob in FIX position doesn't matter as the pot is out of the circuit, so you can set it to 7pm, 12 pm or 3pm, etc. -- it won't make any difference in FIX position.

So I tried the 2 gain settings again and carefully matched the volume, mgoodman is right, I couldn’t really tell a difference…
 
Feb 11, 2022 at 2:44 AM Post #56 of 131

newworld666

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Just got done testing with DCA Stealth and DCA AEON 2 Noire. Both sound great with the Ampersand. Pictures below.

This was probably the most stringent test. I'm happy with the results. Both of these headphones are 13 Ohms, which is very difficult to drive for a portable amp.

These are great headphones and I liked the sound. But sound quality is not what this post is about. As an engineer, I wanted to trip the output protection circuit, so I drove these to the point when the circuit tripped and cut out the power to the amp. Basically, if there is an overload condition, rather than damage the amp and cause the user unnecessary frustration, the system just gracefully shuts off the power. The system recovers as soon as the signal level is lowered and this action is not harmful to the operation of the Ampersand or the headphones. We made sure you don't even hear a click. The amp just goes quiet for a moment and then quickly recovers. With the CANJAM LA prototype, level was adequate, but since then, we made significant improvement before going to production. I tested with the shipping, production Ampersand.

Both headphone models get unbearably loud for my taste. I drove the inputs into clipping so I could see the RED LEDs, switched the gain to MAX and raised the Volume so I could engage the output short circuit protection and it would cut out. Listening levels were so uncomfortably loud at that point that I could only stand about 10 seconds. I would NEVER EVER listen at that level. When I backed the Volume down to the level at which I could listen for more than 10 seconds, the amp performed completely fine.

So here is the list of headphones we successfully tested to date with Production Ampersand:

Aeon 2 Noir, Stealth, Susvara, Ananada, HE-6, HD-800/800s, and HEDD.

I expect more are coming shortly. All preorder units are likely already received by their customers.







With the DCA Stealth I could notice several times that luckily sound was cut out if by mistake volume knob went too far and sound came back as soon the volume was lowered !!!
That's a very good and very important feature ...

As I feel the volume knob is rather far too easy to be moved, I decided to switch the Ampersand on FIX volume out .. That will be less risky with the Sony WM1A as I don't have a fix line-out.
I was expecting that in the box you would include the plastic volume protection we could see on the prototypes when we pre-ordered it, I think it could be necessary if I intend to use the Ampersand with some DAP with true fixed line out..

Is there a way to buy such thing ?




1644565354952.png
 
Feb 11, 2022 at 2:52 AM Post #57 of 131

ChrisLN

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With the DCA Stealth I could notice several times that luckily sound was cut out if by mistake volume knob went too far and sound came back as soon the volume was lowered !!!
That's a very good and very important feature ...

As I feel the volume knob is rather far too easy to be moved, I decided to switch the Ampersand on FIX volume out .. That will be less risky with the Sony WM1A as I don't have a fix line-out.
I was expecting that in the box you would include the plastic volume protection we could see on the prototypes when we pre-ordered it, I think it could be necessary if I intend to use the Ampersand with some DAP with true fixed line out..

Is there a way to buy such thing ?





+1… I was thinking about the same thing too.
 
Feb 11, 2022 at 3:20 AM Post #59 of 131

newworld666

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